Mmh... are the optional load resistor and the 10kΩ resistor above it connected in parallel? If so (I cannot see through the board), you could simply install a 7.15kΩ resistor from the E96 series instead of the 10kΩ one and scrap the additional footprint.

Nice! That adds a bit more flexibility. The 2% tolerance should not be a problem, because they apply to the resistor network as a whole. The resistors within should be closely matched. Also, the 4310R-R2R-104(LF) and 4610X-R2R-104(LF) are interchangeable, which means that only one of them has to be …

Alright! This is the (hopefully) complete schematic of the SoundJr: Filename SoundJr_schematic_messy.png File size 26.64 KiB Views 352 views File comment SoundJr schematic – untested, with components all over the place At this point, I'm not quite sure how it does volume control. It does not …

My basic theory has not changed. Apparently, the NPN transistors pull the additional DAC lines to GND, while the PNP transistors pull them to VCC. The design uses 20kΩ base resistors, as well. The presence of these NPN transistors and base resistors does indeed make perfect sense. EDIT: They might …

Thank you, Cloudschatze! That back side is a bit more crowded than I expected. I see: The expected 8×10kΩ resistor array Four more 10kΩ resistors Three more 20kΩ resistors Two capacitors (filtering?) A 470Ω resistor Another 100Ω resistor Another PNP transistor Four NPN transistors (MMST2222A) And …

Are you sure that R is 200kΩ, or might that be 2R? EDIT: Never mind. You are sure that it's 2R. And yes, the 4310R-R2R-104LF is a 100kΩ part. I'm asking because the Speech Thing uses a resistor network where 2R is 200kΩ, R is 100kΩ and the load resistor 25.5kΩ. It would have made sense for Covox to …

As I was afraid it is not a regular bus network. This network has R-2R ladder inside and can not be easily found online for a reasonable price. :dead: Would it be possible to somehow bodge-solder a Bourns 4310R-R2R-104LF in there? That part is very similar to the one in the Covox Speech Thing but …

matze79 wrote: Who cares about FTL Soundadapter Gameport, it works with nothing. Except Dungeon Master, so its just a Piece of Junk. Patching the keyboard interrupt via TSR driver should do the trick. A "mouse" driver would also be an option.

There's no huge need to use foil capacitors but you should definitely use C0G/NP0 ceramics in the analog inputs section, then it is guaranteed there are no issues and you can keep the footprints. Well, in that case I'll use film capacitors. (I can keep the footprints, either way.) My original plan …

Well, as you can see, I'm not using any specific capacitor type, yet. (It's just computer graphics!) Basically, the design uses six 10nF capacitors. Two of them are just buffers that keep the 2.5V reference voltage stable, four are timing capacitors. I figured that the capacitors' exact properties …

As you probably noticed, it is heavily inspired by IBM's Analog Input Card. Compared to the original, I used ceramics capacitors rather than foil capacitors, SIL instead of DIL resistor packs, the two NE556s instead of a single NE558 and shrunk it down to 10cm × 8cm. Amazingly, the two NE556s …

Any interest in something like this? game_control_adapter.png I'm aware that a game port on its own is not a sound card, but game ports spent the better part of their existence on sound cards, so something like this might still be a nice add-on for someone who only has an Adlib. This one is designed …

God we need someone with a tool for making custom brackets. But yeah, looks lovely! ah i already have a solution for that into mind :) Then also make some for the snark barker!! Would slot bracket No. 9204-1 by Keystone Electronics do? ( mouser link ) Keystone Electronics appears to have quite a …

There is no full schematic for the SoundJr, yet, but a partial one in my second post to this thread. The SoundJr appears to use an 11 bit 10kΩ R-2R ladder (8 data lines + 3 control lines) with an additional control line to disable the entire thing. The three most significant bits are transistor- …

I expect to see at least three more resistors – namely 10kΩ – on the back side of the SoundJr board, that, combined with the three 20kΩ resistors on the front side, extend the R-2R ladder to permit the 8 different volume levels. But we'll see.

Well, it's a good thing then that the internet does not forget, right? He produced a product that had 8 step software volume control, double the frequency range of the Covox Sound Thing, and could directly drive a 32 Ohm pair of headphone due to the integration of a simple amp, and even a sleep-mode …